Freezing is a transient non-equilibrium process, during which phase change occurs with release of latent heat as liquid or fluid cools below freezing temperature due to ambient cooling conditions. When water or some water based-mixtures are cooled below freezing, the material changes from a liquid state to a solid state, and undergoes a significant expansion in volume, which is as much as 10% or more for water or water-based mixtures. When water freezes in a pipe or other confined spaces, its volume expands. Water that has frozen in confined spaces does more than simply clog the pipes and block flow. When freezing occurs in a confined space like a steel pipe, the ice will expand and exert extreme pressure which often leads to bursting of the pipe or separation of a joint and cause serious damage. This phenomenon is a common failure mode in hot-water heating systems and automotive cooling systems.
Ice forming in a confined space does not always cause cracking where ice blockage occurs. Rather, following a complete ice blockage in a confined space, continued freezing and expansion inside the confined space can cause water pressure to increase downstream, which could lead to pipe failure and/or cracking in these areas. Upstream from the ice blockage the water can retreat back towards its inlet source, and there is little pressure buildup to cause cracking. Relative to other liquids, water-based mixtures are preferred for use in liquid cooling systems due to advantages in thermal properties and health and safety concerns.
Liquid cooling systems for electronic devices are occasionally subjected to sub-freezing environments during shipping, storage, or in use. If the liquid freezes, the system must be designed to tolerate any volume expansion that would occur. Additives used to lower the freezing point, such as antifreeze, are potentially poisonous and flammable and can damage mechanical components, sensitive sensors, and electronics.
Therefore, to use pure water or substantially pure water in such a system, an apparatus for and method of controlling freezing nucleation and propagation is needed, such that the system can tolerate the volume expansion caused by freezing of the aforementioned fluid without damaging electronic components or affecting system performance.